<html>
<head>
    <title>Captive Portal</title>
    <style type="text/css">
        body {
            text-align: center;
        }
    </style>
</head>
<body>
    <h1>Captive Portal</h1>
    <form method="post">
        Username: <input type="text" name="username"><br>
        Password: <input type="password" name="password"><br>
        <input type="submit" value="Log in">
    </form>
</body>
</html>